The heater of the related art comprises a rod-shaped ceramic heater including: a ceramic heater body extending in the axial direction and having a heating element at the leading end portion thereof for generating heat when energized; and a pair of energizing lead terminals extending from the heating element and exposed to the outer circumference of the trailing end side of the ceramic heater body. Moreover, the ceramic heater is energized through a core rod arranged on the trailing end side of the ceramic heater in the axial direction and through a metallic lead connecting the core rod and one of the lead terminals of the ceramic heater (as referred to JP-A-2002-364841 (FIG. 1)).